Would lead to significant eccentricity with respect to the sun, probably.
Or, it's been out there quite a while, and has had a few bumps, a brute force, monkeys and typewriters method, during encounters with other minor planets.
But this is unlike other bodies in similar orbits....
Also, I think the article said it was an oblong piece of rock, so perhaps a very high early rotation rate altered the orbit to what is seen today (and therefore the rotation rate is low today).
That would probably require a long-term stay by a nearby large body, though (think about the moon's rotation, which slowed to what it is now by gravity gradient/tidal forces). Not to mention that a slowdown in rotation would not, in itself, have any bearing on the orbit of the body. The orbit and rotation would have had to have been affected by the same perturbing force.
But this is unlike other bodies in similar orbits......each of which has a unique orbit. :') Also, there are more to be discovered, and eventually this "Buffy" oddball could be known as just the first of a whole family of similar objects. That has definitely happened before.